It is common to utilize Hall sensors to determine motor rotor position. Unbuffered Hall sensors generate low amplitude signals that are directly proportional to the motor magnetic field. These signals are sinusoidal and typically in a range of 100 millivolts peak-to-peak. The Hall sensors are typically disposed within the motor housing, increasing the likelihood that the output signal will have electrical noise superimposed thereon.
The effect of noise on the smaller signals produced by Hall sensors can result in drive circuitry producing unwanted multiple drive pulses as the sensor output voltage approaches and crosses zero. One result of multiple pulses as the sensor voltage goes through zero is rattling of the motor stator and output switch overstress as the outputs repetitively switch back and forth between phases during commutation.